West Mercia Police said the arrest came after a tip-off from a member of the public who reported seeing the driver inhaling the substance behind the wheel of a grey Mercedes.
Police said the driver was spotted near Junction 3 (Newent) of the M50, which links the A40 and A49 at Ross-on-Wye with the M5 near Strensham, Worcestershire.
After police pulled the car over, a search uncovered drugs, and the driver tested positive for cannabis.
Officers used the incident to remind the public about the dangers of driving under the influence of drugs, which can impair reaction times, coordination, concentration, and vision.
By law, it is a criminal offence to drive with cannabis in the body above the legal limit.
Convictions for drug driving can result in at least a 12-month driving ban, an unlimited fine, and, in some cases, imprisonment.
A conviction remains on a driving licence for 11 years.
The reclassification of nitrous oxide as a Class C drug in November 2023 means possession for recreational use is now illegal.
Penalties include cautions, fines, or imprisonment for repeat or more serious offenders.
“Our officers can carry out roadside drug tests to detect drivers under the influence of cannabis and cocaine,” police said on Friday (July 24), but did not give a time or date for the arrest.
“We will continue to target dangerous and impaired drivers 24/7 to keep our roads safe.”